1. Field of the Invention
The present invention relates to a method and system for operating cells in an overlay network where macro cells and home cells coexist.
2. Description of the Related Art
With the development of communication technology and the increasing deployment of multimedia technology, a variety of mass transfer technologies have been applied to mobile communication systems, and one of their key issues is an increase in wireless capacity. The increase in wireless capacity may be achieved in various ways. For example, more frequencies may be allocated to increase the wireless capacity, but this is impracticable because of the finiteness of the frequency resources. Therefore, a method of more efficiently using the limited frequency resources is required, and for the efficient use of the limited frequency resources, a method of increasing the frequency utilization efficiency and a method of miniaturizing service cells may be considered. In particular, the cell miniaturizing method can provide a plurality of User Equipments (UEs) with the wireless environment where abundant higher-quality resources are available, thereby enabling high-capacity services.
Unlike the conventional Base Station (BS) or Node B (hereinafter referred to as a ‘macro BS’), a BS, which provides communication services to a small number of UEs existing in a home cell region or a micro communication region such as an independent office, a residence and a building, is defined as a home Node B or a home BS. A plurality of home BSs serving an arbitrary home cell region exist in a macro cell region served by the macro BS. The home cell may connect a mobile phone to the Internet, providing Fixed Mobile Convergence (FMC) services or combined wire/wireless services at low cost.
In the conventional communication system, if powered on by a user, the home BS operates in a receive mode like the UE, instead of transmitting data in a downlink time period, and measures signal strengths of neighbor BSs. Based on the collected information, the home BS determines the neighbor BSs depending on Frequency Assignment (FA), transmit power, and BS information. The neighbor BSs are used to make a list of candidate BSs subjected to handover attempt. The list of neighbor BSs may be set in a manual manner proposed by a mobile network operator, or may be automatically set based on signal measurement.
While the macro BS is installed by the mobile network operator, the home BS is installed or uninstalled by the user, making it difficult for the macro BS to manually update each home BS in its neighbor BS list.
Typically, once installed, a new macro BS generates installation parameters associated with its internal configuration by itself. However, in all operation steps, if the new macro BS identifies neighbor BSs based on only the signals measured by UEs and includes in the neighbor BS list the BSs, measured signals of which satisfy a specific condition, without making a list of initial neighbor BSs, then the home BS is not considered, resulting in the neighbor BS list being inaccurate.
A conventional macro BS is allocated one Physical resource Cell IDentifier (PCID) within a limited range. The PCID allocated to the macro BS should be set not to be identical to those of BSs included in the list of neighbor BSs of the macro BS. However, if the home BS and the macro BS use the same PCID because a PCID of the macro BS is allocated without considering the home BSs, PCID collision may occur between BSs.